arrays - How to store values continuously without overwriting the previous one? -

my project "optical flow estimation flame detection in videos" in while extracting feature values, can retain last intensity value of frame.

here code

function [iy, ix, it] = grad3d(imnew,bfinescale,binitialize) persistent siz gx gg imprev;   if nargin>2 && binitialize   [gx, gg]= makefilters();  if bfinescale     siz = size(imnew);    imprev= single(imnew); else% if ~bfinescale     siz = floor(size(imnew)/2);     %initialize imprev half size     imprev = imresizenn(single(imnew),siz);     end end  if ~bfinescale  imnew = imresizenn(conv2(single(imnew),gg,'same'),siz);  else imnew = single(imnew);  

end

 ix = conv2(gg,gx,imnew + imprev,'same');   iy = conv2(gx,gg,imnew + imprev,'same');   = conv2(gg,gg,imnew - imprev,'same'); %l3 

% finally, store away current image use on next frame imprev = imnew; testfeature = mean(imprev); save testfeature testfeature

[gx, gg]= makefilters() x = (-1:1);  gg = single(gaussgen(0.67,3)); gx = single(-x.*gg*3); 

in highlighted coding(testfeature=mean(imprev)). can able intensity value of last frame extracted...but need values extracted frames. need value stored row wise in matrix file.